The dynamic mechanism of 4E-BP1 recognition and phosphorylation by mTORC1
The dynamic mechanism of 4E-BP1 recognition and phosphorylation by mTORC1
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DOI：
10.1016/j.molcel.2021.03.031
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发表时间：
2021-06-03
期刊：
影响因子：
16
通讯作者：
Hiller, Sebastian
中科院分区：
文献类型：
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作者：
Bohm, Raphael;Imseng, Stefan;Hiller, Sebastian
真核生物中帽依赖性翻译的激活需要通过1 MDa激酶哺乳动物雷帕霉素靶蛋白复合物1（mTORC 1）对4 E-BP进行多位点分级磷酸化。为了在原子水平上解决这种分级磷酸化的机制，我们通过NMR光谱监测了固有无序的4 E结合蛋白亚型1（4 E-BP 1）与mTOR（Raptor）的mTORC 1亚基调节相关蛋白的相互作用。4 E-BP 1的N-末端RAIP基序和C-末端TOR信号传导（TOS）基序结合Raptor中的不同位点，导致4 E-BP 1的基于亲合力的拴系。这种束缚使4 E-BP 1的柔性中心区域朝向用于磷酸化的mTORC 1激酶位点。由两种束缚相互作用施加的结构约束，结合磷酸化诱导的4 E-BP 1构象转换，解释了mTORC 1对4 E-BP 1磷酸化的层次结构。此外，我们证明mTORC 1识别游离和eIF 4 E结合的4 E-BP 1，允许整个4 E-BP 1库的快速磷酸化和翻译的有效激活。最后，我们的研究结果提供了一个机制解释的差异雷帕霉素敏感性的4 E-BP 1磷酸化位点。
The activation of cap-dependent translation in eukaryotes requires multisite, hierarchical phosphorylation of 4E-BP by the 1 MDa kinase mammalian target of rapamycin complex 1 (mTORC1). To resolve the mechanism of this hierarchical phosphorylation at the atomic level, we monitored by NMR spectroscopy the interaction of intrinsically disordered 4E binding protein isoform 1 (4E-BP1) with the mTORC1 subunit regulatory-associated protein of mTOR (Raptor). The N-terminal RAIP motif and the C-terminal TOR signaling (TOS) motif of 4E-BP1 bind separate sites in Raptor, resulting in avidity-based tethering of 4E-BP1. This tethering orients the flexible central region of 4E-BP1 toward the mTORC1 kinase site for phosphorylation. The structural constraints imposed by the two tethering interactions, combined with phosphorylation-induced conformational switching of 4E-BP1, explain the hierarchy of 4E-BP1 phosphorylation by mTORC1. Furthermore, we demonstrate that mTORC1 recognizes both free and eIF4E-bound 4E-BP1, allowing rapid phosphorylation of the entire 4E-BP1 pool and efficient activation of translation. Finally, our findings provide a mechanistic explanation for the differential rapamycin sensitivity of the 4E-BP1 phosphorylation sites.